Yup, typically it is roast beef. And as you say, it is a gravy bowl. Basically just sits on the plate next to the roast potatoes or whatnot and you fill it with gravy as well as having gravy on the ret of the plate. Some like to keep it crispy, but i like it with gravy, as most do, so that it just becomes a soggy mess of beef flavoured batter. Yunmmy! If it's not a round pudding in a bowl shape, then it simply isn't a yorkshire pudding
Like so
Roast beef just isn't roast beef without a yorkshire pudding or 2
Another tip. If a roast dinner is a regular thing, or simply roast potatoes, then really good thing, like with the "science" of not frequently hanging the oil in a deep fat fryer, once you have cooked the potatoes in the oil with garlic and herbs, strain the old oiul through a sieve and refrigerate it till next time. Means that you're then cooking the next batch of potatoes in oil that is full of flavour
They just get better and better
If you're gonna do it in the method given by alotapot, then you're better of putting the batter into a high sided roasting tray, and throwing in loads of sausages. Voila, you have toad in the hole. another staple unhealthy british fav